Urinary extravasation (UE) in patients with posterior urethral valves (PUV), in the form of urinomas or urinary ascites, is thought to represent a pop-off mechanism. Previous literature has proposed a kidney protective mechanism, although this remains controversial. Here, we performed a matched comparison to assess the effect of UE on kidney outcomes.

We retrospectively reviewed our PUV database, including all patients diagnosed < 3 months of age with at least 1-year follow-up. We collected demographics, management, vesicoureteral reflux (VUR) status, and kidney function parameters. UE was defined as postnatal urinoma or urinary ascites. We performed both unadjusted and propensity-matched comparisons of patients with and without UE. Matching was used to balance age, diversion status, urinary tract infection history, presence of VUR, and nadir creatinine. The primary outcomes were 1-, 3-, and 5-year kidney outcomes.

Of the 138 patients meeting inclusion criteria, 27 (20%) had UE (23 urinoma, 4 urinary ascites). The median age at presentation was 5 days. Six patients (26%) required percutaneous drainage, and the median time to resolution was 21 days. Patients with UE had significantly higher initial creatinine levels but no difference in nadir values. Of those with available data, 18 (18%) and 10 (14%) had chronic kidney disease (CKD) at 3 and 5 years. Overall, there was no difference in 3- and 5-year rates of CKD between patients with and without a history of UE.

In a matched comparison, UE was not associated with long-term adverse or beneficial effects on kidney function. This study provides further evidence that the presence of UE may not be a relevant prognostic factor in children with PUV.